The reason that I asked John, is that both UNC & BSW both have the same diameter and pitch (but different thread angles) and sometimes, at a push, can be used with each other as a 'get you home' fix (bodge it up).

So I just asked which thread type it was, just to make sure that the correct information is given, so that people could buy the right ones, and not have to bodge the bolts in.

We will have to differ on the best threads (there has been massive debates on the subject), as sometimes, both the coarse threads of UNC & BSW can be used to great effect when trying to hold a thread in soft or weak materials, like ali, sometimes brass and bronze(depending on type), tufnol and magnesium etc, whereas metric will just strip out when tightening pressure is applied, as the threads are not strong enough.

BTW, if you buy the slightly more expensive versions of the 3-2-1 blocks (in a plastic blow moulded box), they are supplied with the correct sized cap screws, but they still won't go thru the blank holes. I know, I have bought both types.

John